A disc rotor is known which includes a sliding portion, a hat portion and connecting units. The sliding portion, formed into a substantially ring-shape, is sandwiched between friction pads at the time of a braking operation. The hat portion is made of a metal material (an aluminum alloy) that is softer than a metal material (an iron-series material), of which the sliding portion 11 is made. The hat portion is connected to a radially inner portion of the sliding portion at a radially outer portion thereof. The hat portion includes an inner flange portion, at which the hat portion is fixed to a wheel hub. Each of the connecting units is arranged at a connecting portion of the sliding portion and the hat portion so as to integrally connect the sliding portion and the hat portion.
According to JP2004-530848T, each of the connecting units includes a sheet-shaped insert, a block-shaped drive element, a flat spring and a screw. The insert is accommodated in a radial recess formed at a radially outer portion of the hat portion (corresponding to a bell in JP2004-530848T). The flat spring is attached to an end of the drive element facing the hat portion. The screw is inserted through a radially inner portion of the sliding portion (corresponding to a braking band in JP2004-530848T), the drive element, and the flat spring in the radial direction of the rotor, so that the sliding portion, the drive element and the flat spring are fastened by means of a nut and the screw.
According to the above-described connecting units in JP2004-530848T, although a desired level of strength may be obtained, assembly may not be easy since each of the connecting units includes multiple members (five members): the insert, the drive element, the flat spring, the screw, the nut and the like. Further, according to the above-described connecting units, the inserts are made of a wear-resistant sheet metal, such as spring steel and the like, which is a dissimilar metal from the material of the hat portion (an aluminum alloy). In a state where the inserts are arranged at the corresponding radial recesses of the hat portion (i.e. in a state where the inserts are not yet screwed into the radial recess of the hat portion by means of the nuts and the bolts), a gap may be formed (i.e. a gap for easy assembly of the inserts to the hat portion) between the inserts and the hat portion in the axial, radial and circumferential directions of the rotor. Even after the inserts have been screwed into the hat portion by means of the nuts and the bolts, the gap remains between the inserts and the hat portion in the radial and circumferential direction of the rotor. As a consequence, ingress of liquid may occur, which may result in bimetallic corrosion (galvanic corrosion). Furthermore, according to the above-described connecting units, the nuts and end portions of the screws protrude from the radially outer portion of the hat portion in the axial direction of the rotor. Therefore, a length of the connecting units increases in the axial direction of the rotor, and a room necessary to assemble the connecting units increases.
A need thus exists for a disc rotor that is not susceptible to the drawback mentioned above.